This study numerically investigated the condensation heat transfer and flow characteristics of refrigerant R134a in a rectangular minichannel. Three-dimensional simulations were carried out at different mass fluxes, vapor qualities, and gravity conditions using the volume-of-fluid (VOF) model, a turbulence model, and a phase transition model. The effects of various parameters on the surface heat transfer coefficient and the frictional pressure gradient are investigated. The condensation process was found to be enhanced due to the increase of vapor quality and mass flow rate, while the frictional pressure gradient was found to decrease with the decrease of vapor quality and mass flow rate. Simulation results revealed that the liquid film tends to accumulate along the corner of the cross section of the minichannel. Furthermore, the thickness of the liquid film was found to increase with the decrease of mass flux and vapor quality.